Surgical stents have long been known which can be surgically implanted into a body lumen, such as an artery, to reinforce, support, repair or otherwise enhance the performance of the lumen. For instance, in cardiovascular surgery it is often desirable to place a stent in the coronary artery at a location where the artery is damaged or is susceptible to collapse. The stent, once in place, reinforces that portion of the artery allowing normal blood flow to occur through the artery. One form of stent which is particularly desirable for implantation in arteries and other body lumens is a cylindrical stent which can be radially expanded from a first smaller diameter to a second larger diameter. Such radially expandable stents can be inserted into the artery by being located on a catheter and fed internally through the arterial pathways of the patient until the unexpanded stent is located where desired. The catheter is fitted with a balloon or other expansion mechanism which exerts a radial pressure outward on the stent causing the stent to expand radially to a larger diameter. Such expandable stents exhibit sufficient rigidity after being expanded that they will remain expanded after the balloon has been removed.
Radially expandable stents come in a variety of different configurations to provide optimal performance in various different particular circumstances. For instance, the patents to Lau (U.S. Pat. Nos. 5,514,154, 5,421,955, and 5,242,399), Baracci (U.S. Pat. No. 5,531,741), Frantzen (U.S. Pat. Nos. 5,718,713, 5,741,327, 5,746,691), Gaterud (U.S. Pat. No. 5,522,882), Gianturco (U.S. Pat. Nos. 5,507,771 and 5,314,444), Termin (U.S. Pat. No. 5,496,277), Lane (U.S. Pat. No. 5,494,029), Maeda (U.S. Pat. No. 5,507,767), Marin (U.S. Pat. No. 5,443,477), Khosravi (U.S. Pat. No. 5,441,515), Jessen (U.S. Pat. No. 5,425,739), Hickle (U.S. Pat. No. 5,139,480), Schatz (U.S. Pat. No. 5,195,984), Fordenbacher (U.S. Pat. No. 5,549,662), and Wiktor (U.S. Pat. No. 5,133,732), each include some form of radially expandable stent for implantation into a body lumen. Other prior art stents are compiled in the Handbook of Coronary Stents, Second Edition, produced by the Rotterdam Thoraxcenter Interventional Cardiology Group.
Most of these prior art stents suffer from undesirable axial contraction when radially expanded. Stents can be made to resist axial contraction upon radial expansion by including axial elements therein extending continuously from a first end of the stent to a second end of the stent. However, such continuous axial elements tend to make the stent stiff and exhibit less flexibility characteristics than needed to allow the stent to be easily passed through tortuous arterial pathways or other tightly curving body lumens effectively. Some of these prior art stents, such as the stents described in the patents to Frantzen resist axial contraction upon radial expansion by locating axial elements offset from each other and within troughs of adjacent circumferential elements. While flexibility does improve somewhat by offsetting such axial elements, additional flexibility is often needed.
In addition to flexibility drawbacks, known prior art stents typically are provided with a pre-configured contour having various different pre-radial expansion and post radial expansion diameters. These prior art stents have other non-variable predetermined characteristics such as strength characteristics, radiopacity characteristics, biocompatibility characteristics, flexibility characteristics and axial length characteristics. Body lumens in which stent implantation is indicated can vary in a variety of different ways. Hence, pre-configured stents are not always provided with a contour and other characteristics which optimally match the needs of the body lumen where implantation is desired. Accordingly, a need exists for a stent which can be custom configured by the surgeon or custom ordered by the surgeon for ready assembly by a qualified technician to the surgeon's specifications to provide the treatment desired within the body lumen where implantation of the stent is to occur.
Also, stent flexibility of known prior art stents is not well matched with flexibility of stent delivery and expansion balloons. Rather, known stent delivery and expansion balloons typically are provided with a cylindrical contour which can be inflated and radially expanded to just a few different radial sizes. Accordingly, a need exists for a balloon which can be configured to have flexibility and radial expansion characteristics which more closely match the flexibility and radial expansion characteristics of stents with which the balloon is mated.